Fix [ocba:...] not to look like [ocb:...].

Supposedly starting with the addition of 161 to glyph encodings [ocba:1;3mm] looks like [ocb:1;3mm] - the accentus is not printed.
Wonder if
\def\grelinea#1#2#3{%
  \greglyph{\char 87}{#1}{#2}{#3}{}{}%
  \relax %
}
doesn't need similar treatment, but there is nothing in gregorio-chars.tex for it and I don't know how to test it.